src\m1\module-info.java:4: error: module not found: m2
    requires m2;
             ^
error: cannot access module-info
  cannot resolve modules
javadoc: error - fatal error encountered: java.lang.AssertionError
javadoc: error - Please file a bug against the javadoc tool via the Java bug reporting page
(http://bugreport.java.com) after checking the Bug Database (http://bugs.java.com)
for duplicates. Include error messages and the following diagnostic in your report. Thank you.
java.lang.AssertionError
at jdk.compiler/com.sun.tools.javac.util.Assert.error(Assert.java:155)
at jdk.compiler/com.sun.tools.javac.util.Assert.check(Assert.java:46)
at jdk.compiler/com.sun.tools.javac.comp.Modules.enter(Modules.java:248)
at jdk.javadoc/jdk.javadoc.internal.tool.JavadocTool.getEnvironment(JavadocTool.java:194)
at jdk.javadoc/jdk.javadoc.internal.tool.Start.parseAndExecute(Start.java:591)
at jdk.javadoc/jdk.javadoc.internal.tool.Start.begin(Start.java:424)
at jdk.javadoc/jdk.javadoc.internal.tool.Start.begin(Start.java:341)
at jdk.javadoc/jdk.javadoc.internal.tool.Main.execute(Main.java:63)
at jdk.javadoc/jdk.javadoc.internal.tool.Main.main(Main.java:52)
4 errors